The present invention seeks to provide a heat and sound insulating casing brick having a frame-like or hollow insulating insert, that is to say a building brick which serves as permanent shuttering for a supporting core of concrete poured into it, thus permitting the construction of heat and sound insulating walls.
Casing bricks of this type are usually made of light-weight concrete incorporating heat insulating additives, for example wood shavings and other fibrous material, expanded clay, or perlite. It is also known for insulating sheets of synthetic foam material to be applied to the longer sides of the cavity within the insert. All previously known casing bricks, however, have the disadvantage that the shorter side walls form cold bridges extending from outside to inside of a wall formed therefrom.
According to one aspect of the present invention, there is provided a casing brick comprising a hollow insulating insert, and a two-part concrete shell which substantially encloses the insert, two projections extending from the insert and positioned between the two parts of the shell and interlocking projections and grooves for connecting the shell and the insert together.
Owing to the fact that, in one embodiment of the invention, about half the volume of the casing brick consists of expanded plastics material, particularly advantageous heat insulation values are obtained. The shell serves to protect the insert against mechanical damage, to form a strong impact surface, and to take rendering or other covering. Due to the fact that each of the two parts of the shell are separated by the projections extending from the insert, it is possible to arrange that no heat bridge is formed between the inside and outside of a wall built from the casing bricks which is of decisive importance for heat insulation.
According to another aspect of the present invention there is provided a method of making a casing brick comprising the steps of inserting a hollow insulating insert into a hollow mould which is open at opposite ends and has an outer wall part and an inner wall part, the inner wall part forming a lining for the interior of the insert, and pouring concrete mixture into a cavity between the insert and the said outer wall part.
The present invention also seeks to provide an apparatus for making casing building bricks of this type. The manufacture of casing bricks requires particular care, because of the relatively low breaking strength of the insert, particularly if it is of expanded plastics material. This relatively low breaking strength makes it impossible for the insert to be used as shuttering for the casting of the shell unless special precautions are taken. As will be appreciated pressure applied to the insert during casting of the shell would very easily result in the fracture of the insert.
According to a further aspect of the present invention, there is provided an apparatus for making casing bricks comprising a hollow mould consisting of an outer wall body whose dimensions correspond to the outside dimensions of the casing brick which is to be produced, and an inner wall body inserted therein, the inner wall body having a height at least equal to the height of an insulating insert arranged to fit into the interior of the inner wall body to define a cavity between the insert and the outer wall body for the reception of a concrete mixture which, when set, forms a concrete shell substantially enclosing the insert.
Preferably, said inner wall body tapers conically and the insert has internal walls which taper correspondingly.